Our staff maintains and operates a battery of sophisticated solution-based biophysical instrumentation. Among the analytical methods available to intramural researchers are: analytical ultracentrifugation (AUC), isothermal titration calorimetry (ITC), surface plasmon resonance (SPR), differential scanning calorimetry (DSC), dynamic light scattering (DLS), circular dichroism spectroscopy (CD), and asymmetric flow field-flow fractionation (AF4). Accuracy and precision in AUC are critical to properly characterize protein samples. Our collaboration with Peter Schuck and Huaying Zhao resulted in the development of new devices to monitor temperature measurements of the rotor and accurate determinations of the radial magnification of the optic systems. Ultra-small gold nanoparticles are especially attractive in applications requiring delivery to crowded intracellular spaces in the cytosol and nucleus of cells. In collaboration with the Laboratory of Cellular Imaging and Macromolecular Biophysics of the NIBIB, we have used AUC and DLS to characterize the size-distribution of MBA and GSH stabilized ultrasmall gold particles in buffers with and without Fetal Bovine Serum (FBS). Using AUC, DLS and ITC, we continue to explore the size, shape and self association properties of various protein systems. Collaborative projects with NIAID led to exploratory AUC work on oligomeric states of wild type and mutant polypeptide constructs of NSP5, helped characterize individual proteins like DBL2x, PfCSA-pcm2 and their mixtures to answer questions regarding high affinity binding between these species and allowed us to continue our investigations into the study of the different oligormeric properties of several forms of serum amyloid A (SAA). In collaboration with NIDDK, we have studied the purity and self-association characterization of mutant RNA polymerase and investigated the crowding effect on riboswitch conformation of TMAO by measuring diffusion coefficients.